NWSP 80.6 Water Resistance (Hydrostatic Pressure)

Standard:

NWSP

Method:

NWSP 80.6

Title:

Evaluation of Water Resistance (Hydrostatic Pressure) Test

Scope

The NWSP 80.6 Water Resistance test applies to any nonwoven fabrics, which are intended for use as a barrier to the penetration of fluids. This test measures the resistance of nonwoven fabrics to the penetration of water under varied hydrostatic head pressures.

When testing some fabrics, such as meltblown fabrics, a nylon web or net screen may be used to support the specimen. This would simulate the effect from a bonded laminate and prevent the weight of the water from tearing or stretching the material. If this technique is used it must be reported with the test results.

The SI values are regarded as the official standard system of measurement for this standard test method. If other systems of measurement are used in place of SI units (including inch-pound) their values must be reported independently. Systems of measurement must not be combined in any way, but shall be regarded and reported separately.

Principle

A nonwoven fabric specimen is mounted to form the cover on the test head reservoir. This specimen is subjected to a standardized water pressure increase at a constant rate until leakage appears on the outer surface of the nonwoven. The test results for the hydrostatic water pressure test are measured at the point where the first drops appear in three separate areas on the specimen. The results can be reported in either centimeters per minute or millibars per minute. Ignore any drops which form within 6 mm from the edge of the clamp; these drops may be due to the clamping process. If numerous drops form at the edge of the clamp, repeat the test with another specimen. If a water spout is formed from one of the penetrating holes, according to the criteria, that is still only one hole.

The rate of increase of the water pressure must be 10 ± 0.5 cm or 60 ± 3 cm H2O/min. Using these two different rates may give different end results. It is important to list in the test results which rate was used.

Do not take into account very fine droplets, which do not grow after being formed and do not count subsequent drops that penetrate through the same location in the nonwoven.

The water pressure may be applied to the test specimen from the below or above. The method used should be stated in the test report.

All standard tests are carried out using the 100 cm2 test head. But, where there are size limitations on the specimens, the 26 cm2 or the 10 cm2 test heads may be used in experimental testing. The different test heads will provide different results and the results should be used only as a relative ranking of materials.

Performance specifications for industrial, medical, and military fabrics have been prepared on the basis of resistance to water penetration and are used in the purchase of fabrics where resistance to water penetration is of interest.

Construction factors and finishing techniques can have an appreciable effect on a finished product’s resistance to penetration of water. The quality of seams and stitching may influence the results.

A higher value indicates greater resistance to water penetration.

Samples

The customer must specify the test side. IPS conditions the samples at 65% RH and 21°C and tests them at 50% RH and 23°C.